1. Field of the Invention
The present invention relates to an ink cartridge, which contains ink, and an ink jet printer for printing by jetting the ink from the ink cartridge onto recording paper.
2. Description of Related Art
A communicating system such as a facsimile system and an information processing system such as a personal computer are usually connected with a printer that is capable of printing data including characters and graphics onto recording paper as visual information. Various printing systems, such as an impact system, a thermosensitive system and an ink jet system, are used for recording. In recent years there has been in widespread use an ink jet printer that uses the ink jet system capable of achieving quiet printing on recording papers produced of various kinds of materials.
The ink jet printer described above is designed to achieve printing onto the entire surface of recording paper. The printing process includes repeatedly printing one band of characters by emitting ink supplied from an ink cartridge to a print head on the recording paper while traversing the print head in a main scanning direction and then moving the recording paper in the direction of sub-scanning for one band width. In this type of ink jet printer, which makes the above-described operation for printing, the ink cartridge is filled with a piece of foam soaked with the ink in order to obtain good printing quality with insured stabilized ink supply to the print head. Further, an ink sensor is employed to detect the presence or absence of the ink for the purpose of predetecting ink depletion in order to prevent defective printing.
That is, in a prior art ink cartridge 51 shown in FIG. 1, an air communicating port 51B and an ink filler port 51C are formed in the top and bottom walls respectively. An electrode 54 is installed as an ink sensor in a space 53 defined by a rib 51A between a wall surface of the ink cartridge 51 and a foam 52. Ink is charged to the foam 52 and the space 53 in the ink cartridge 51 through the ink filler port 51C. By this, the ink supply from the foam 52 is stabilized and ink depletion can be detected with the electrode 54.
In the prior art design described above, however, it becomes necessary to close the ink filler port 51C by a plug member 55 to prevent ink leakage from the ink filler port 51C after the ink is filled in the ink cartridge 51. To reduce the total manufacturing cost, it is desirable to decrease the number of component parts by removing the plug member 55 and the electrode 54 without adversely affecting such functions as the prevention of ink leakage and the detection of ink depletion.